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CCDCONFIG(8) FreeBSD System Manager's Manual CCDCONFIG(8)
NAMEccdconfig -- configuration utility for the concatenated disk driver
SYNOPSISccdconfig [-cv] ccdileave [flags] dev...ccdconfig-C [-v] [-fconfig_file]
ccdconfig-u [-v] ccd...ccdconfig-U [-v] [-fconfig_file]
ccdconfig-g [ccd...]
DESCRIPTION
The ccdconfig utility is used to dynamically configure and unconfigure
concatenated disk devices, or ccds. For more information about the ccd,
see ccd(4).
The options are as follows:
-c Configure a ccd. This is the default behavior of ccdconfig.
-C Configure all ccd devices listed in the ccd configuration file.
-fconfig_file
When configuring or unconfiguring all devices, read the file
config_file instead of the default /etc/ccd.conf.
-g Dump the current ccd configuration in a format suitable for use
as the ccd configuration file. If no arguments are specified,
every configured ccd is dumped. Otherwise, the configuration of
each listed ccd is dumped.
-u Unconfigure a ccd.
-U Unconfigure all ccd devices listed the ccd configuration file.
-v Cause ccdconfig to be verbose.
A ccd is described on the command line and in the ccd configuration file
by the name of the ccd, the interleave factor, the ccd configuration
flags, and a list of one or more devices. The flags may be represented
as a decimal number, a hexadecimal number, a comma-separated list of
strings, or the word ``none''. The flags are as follows:
CCDF_UNIFORM 0x02 Use uniform interleave
CCDF_MIRROR 0x04 Support mirroring
CCDF_NO_OFFSET 0x08 Do not use an offset
CCDF_LINUX 0x0A Linux md(4) compatibility
The format in the configuration file appears exactly as if it were
entered on the command line. Note that on the command line and in the
configuration file, the flags argument is optional.
#
# /etc/ccd.conf
# Configuration file for concatenated disk devices
#
# ccd ileave flags component devices
ccd0 16 none /dev/da2s1 /dev/da3s1
The component devices need to name partitions of type FS_BSDFFS (or
``4.2BSD'' as shown by disklabel(8)).
If you want to use the Linux md(4) compatibility mode, please be sure to
read the notes in ccd(4).
FILES
/etc/ccd.conf default ccd configuration file
EXAMPLES
A number of ccdconfig examples are shown below. The arguments passed to
ccdconfig are exactly the same as you might place in the /etc/ccd.conf
configuration file. The first example creates a 4-disk stripe out of
four scsi disk partitions. The stripe uses a 64 sector interleave. The
second example is an example of a complex stripe/mirror combination. It
reads as a two disk stripe of da4 and da5 which is mirrored to a two disk
stripe of da6 and da7. The last example is a simple mirror. The 2nd
slice of /dev/da8 is mirrored with the 3rd slice of /dev/da9 and assigned
to ccd0.
# ccdconfig ccd0 64 none /dev/da0s1 /dev/da1s1 /dev/da2s1 /dev/da3s1
# ccdconfig ccd0 128 CCDF_MIRROR /dev/da4 /dev/da5 /dev/da6 /dev/da7
# ccdconfig ccd0 128 CCDF_MIRROR /dev/da8s2 /dev/da9s3
The following are matching commands in Linux and FreeBSD to create a
RAID-0 in Linux and read it from FreeBSD.
# Create a RAID-0 on Linux:
mdadm --create --chunk=32 --level=0 --raid-devices=2 /dev/md0 \
/dev/hda1 /dev/hdb1
# Make the RAID-0 just created available on FreeBSD:
ccdconfig -c /dev/ccd0 32 linux /dev/ad0s1 /dev/ad0s2
When you create a new ccd disk you generally want to fdisk(8) and
disklabel(8) it before doing anything else. Once you create the initial
label you can edit it, adding additional partitions. The label itself
takes up the first 16 sectors of the ccd disk. If all you are doing is
creating file systems with newfs, you do not have to worry about this as
newfs will skip the label area. However, if you intend to dd(1) to or
from a ccd partition it is usually a good idea to construct the partition
such that it does not overlap the label area. For example, if you have A
ccd disk with 10000 sectors you might create a 'd' partition with offset
16 and size 9984.
# disklabel ccd0 > /tmp/disklabel.ccd0
# disklabel -Rr ccd0 /tmp/disklabel.ccd0
# disklabel -e ccd0
The disklabeling of a ccd disk is usually a one-time affair. If you
reboot the machine and reconfigure the ccd disk, the disklabel you had
created before will still be there and not require reinitialization.
Beware that changing any ccd parameters: interleave, flags, or the device
list making up the ccd disk, will usually destroy any prior data on that
ccd disk. If this occurs it is usually a good idea to reinitialize the
label before [re]constructing your ccd disk.
RECOVERY
An error on a ccd disk is usually unrecoverable unless you are using the
mirroring option. But mirroring has its own perils: It assumes that both
copies of the data at any given sector are the same. This holds true
until a write error occurs or until you replace either side of the mir-
ror. This is a poor-man's mirroring implementation. It works well
enough that if you begin to get disk errors you should be able to backup
the ccd disk, replace the broken hardware, and then regenerate the ccd
disk. If you need more than this you should look into external hardware
RAID SCSI boxes, RAID controllers (see GENERIC), or software RAID systems
such as geom(8) and vinum(8).
SEE ALSOdd(1), ccd(4), disklabel(8), fdisk(8), rc(8), vinum(8)HISTORY
The ccdconfig utility first appeared in NetBSD 1.0A.
BUGS
The initial disklabel returned by ccd(4) specifies only 3 partitions.
One needs to change the number of partitions to 8 using ``disklabel-e''
to get the usual BSD expectations.
FreeBSD 10.1 July 17, 1995 FreeBSD 10.1